Centrifugal pump



2 Sheets-Sheet 1 Filed Aug. 25, 1967 INVENTOR RICHARD AYSON BY Q 9 MjwATTORNEYS Dec. 3 1968 AYSON 3,

CENTRIFUGAL PUMP Filed Aug 25, 1967 2 Sheets-Sheet 2 FIGZ FIGS

INVENTOR RICHARD AYSON BY Cw ATTORNEYS United States Patent 3,413,926CENTRIFUGAL PUMP Richard Ayson, Aurora, Ill., assignor to General SignalCorporation, a corporation of New York Filed Aug. 25, 1967, Ser. No.663,317 1 Claim. (Cl. 103--111) ABSTRACT OF THE DISCLOSURE A centrifugalpump employing a taper fit between the impeller and drive shaft, and aseal sleeve for protecting the shaft from the wearing effects of theshaft seal. The sleeve is slidable on the shaft and is biased intoabutment with the impeller by a dished ring spring made of coiled flatwire and seated in an annual peripheral groove formed in the shaft.

Background and summary of the invention This invention relates tocentrifugal pumps, and particularly to centrifugal pumps employing ataper fit between the impeller and the drive shaft.

In the conventional centrifugal pump, the end of the drive shaft withinthe volute chamber is provided with a cylindrical portion on which ismounted an impeller which contains a matching cylindrical bore. The pumpincludes a seal device, of either the mechanical or packing box type,which retards leakage from the volute chamber along the shaft, and,since this device, or foreign particles lodged between it and the shaft,can score and Wear the shaft, it is customary to encircle the shaft witha replaceable protective sleeve. The sleeve is keyed to the shaft and isclamped between the rear surface of the impeller and a shoulder on theshaft when the impeller lock nut is tightened to force the impellerlongitudinally along the shaft. With this arrangement, accumulatedmanufacturing tolerances present no problem since the impeller is freeto assume whatever longitudinal position is necessary in order to insurea tight clamp up between the shaft shoulder and the lock nut.

When the conventional pump is in service, the pumped medium sometimesleaks into the small radial clearance between the shaft and the impellerand corrodes the mating surfaces of these parts. This increases theresistance to sliding of the impeller along the shaft and makes itdifficult to remove the impeller from the shaft. In cases where thelength-to-diameter ratio of the impeller bore is large, removal requiresthe use of special wheel pullers. This problem can be eliminated byemploying a taper fit between the impeller and the shaft, since slightaxial displacement of the impeller relatively to the shaft will separatethe impeller from its seat, but, in the past, this solution has entailedelimination of the shaft sleeve. The reason for this is that the finalposition of the impeller relative to the shaft cannot be varied toaccommodate manufacturing tolerances. Unless impractical tolerances areused, there is no way to guarantee both positive seating of theimpeller, i.e., metal-to-metal contact between the tapered shaft portionand the wall of the tapered impeller bore, and firm clamping of theshaft sleeve between the shaft shoulder and the impeller. Sincetolerance buildup in one sense would prevent positive seating of theimpeller, and build-up in the opposite sense would give the sleevefreedom to oscillate along the shaft, it is evident that theconventional shaft sleeve arrangement cannot be used in a pump employinga taper fit between impeller and shaft.

The object of this invention is to provide an improved centrifugal pumpincorporating both a taper fit between the impeller and the shaft, and aprotective seal sleeve 3,413,926 Patented Dec. 3, 1968 for the shaft. Inaccordance with the invention, the seal sleeve is biased into abutmentwith the impeller by a dished ring spring formed of flat wire coiled onedge and seated in an annular peripheral groove formed in the shaft. Theforce and deflection characteristics of this type of spring have beenfound adequate to maintain a satisfactory static seal between the sleeveand the impeller while affording to the sleeve the degree of freedomrequired to accommodate tolerance accumulations. Since the sleeve in theimproved pump is not part of a rigid connection between the impeller andthe shaft, but is biased by a controlled force against the impeller,proper seating of the impeller on the shaft is guaranteed, anddetrimental oscillations of the seal sleeve are precluded.

Description of preferred embodiment The preferred embodiment of theinvention is described herein with reference to the accompanyingdrawings in which:

FIG. 1 is an axial sectional view of a typical horizontal axiscentrifugal pump incorporating the invention.

FIG. 2 is an enlarged view of the shaft seal shown in FIG. 1.

FIG. 3 is an enlarged sectional view showing the installation of thering spring.

FIG. 4 is a perspective view of the ring spring.

As shown in FIG. 1, the improved pump comprises a conventional casing11, cover 12, adapter 13, power frame 14, base 15 and support 16, all ofwhich are held together by bolts, Casing 11 encloses a volute chamber 17which is provided with an axial inlet 18, and which contains theimpeller 19. The impeller is formed with a tapered axial bore whichmatches and receives the tapered inner end of drive shaft 21, and theimpeller and shaft are clamped together by a lock nut 22 which isthreaded onto a stud 23 carried by the shaft, and which acts on theimpeller through a washer 24. Gaskets 25 and 26, inter-posed betweenlock nut 22 and washer 24 and between washer 24 and impeller 19, prevententry of the pumped medium into the impeller bore. A key 27 provides apositive drive connection between shaft 21 and impeller 19.

An insert 28, bolted to adapter 13, carries sealing device 29 whichprevents leakage from volute chamber 17 along drive shaft 21. Thesealing device 29 may be a mechanical seal or, as shown, a stackedseries of packings. In either case, the seal device includesaprotective, replaceable sleeve 31 which is free to slide along, butkeyed to rotate with, drive shaft 21. At its right end, sleeve 31carries an O-ring gasket 32 which is forced against the hub of impeller19 by a ring spring 33 which reacts between drive shaft 21 and the leftend of the sleeve. This spring 33 has a dished shape and is formed froma length of steel wire of rectangular cross section which is coiled onedge. It is seated in an annular groove 34 formed in the periphery ofshaft 21. A suitable, commercially available spring of this type ismarketed by the Ramsey Corporation under the :name Spirolox. Thelaminated construction of ring 33 permits large deflections withoutoverstressing, but, in order to avoid localized yielding, the right wallof groove 34 is inclined or chamfered as shown in FIG. 3.

Spring ring 33 exerts a controlled force on sleeve 31 which, because ofthe substantially continuous zone of engagement, is distributedsubstantially uniformly around the circumference of the sleeve. Themagnitude of the controlled force can be varied by changing thethickness of the material from which ring 33 is made, or by changing thenumber of turns. This controlled force insures positive compression ofthe static seal defined by O-ring 32, and thus renders the sealeffective to prevent the pumped medium from contacting shaft 21.

Although I have illustrated and described one specific embodiment of theinvention, it will be understood that the invention can be employed invarious other types of centrifugal pumps.

I claim:

1. A centrifugal pump characterized by (a) a drive shaft having atapered end portion on which is mounted an impeller containing amatching tapered bore;

(b) a sleeve slidable on but fixed to rotate with the shaft and servingto protect the shaft from the Wearing eifects of a seal mechanism whichencircles the shaft and is arranged to prevent leakage along the shaft;

(c) an annular peripheral groove formed in the shaft;

and

HENRY F.

References Cited UNITED STATES PATENTS Wiltley 103-115 McHugh 287--53Caserta 287-53 Carter 103115 Sence 103-115 RADUAZO, Primary Examiner.

